As a federal judge in Iowa prepares to sentence the orthodox Jewish owner of what once was the nation's largest kosher meatpacking plant, ABC News has learned the details of a quiet campaign to paint his fraud prosecution as "mean-spirited" and the recommended life sentence as "vindictive and excessive."

Five former U.S. Attorneys General have written letters to the judge in defense of the plant owner, Sholom Rubashkin. Former U.S. Rep. Bob Barr has penned an op-ed in the Des Moines Register deriding the proposed life sentence for a fraud that paled in scope to Bernie Madoff's $65 billion, decades-long Ponzi scheme. And the Anti-Defamation League, among others, wrote to the Justice Department with alarm about "troubling" signs that prosecutors deemed Rubashkin a flight risk merely by virtue of the fact that he is Jewish, and thus could escape to Israel.

"Our sense is that the call for a life sentence is completely disproportionate," said Alyza D. Lewin, Rubashkin's attorney, in an interview. "This is a first-time, non-violent offender. He has 10 children. One of them is severely autistic. He has done tremendous charitable work. To suggest that his activities warrant life in prison, where you put murderers, people who represent an ongoing threat to society, it makes no sense."

Prosecutors reject the notion that Rubashkin is in any way a sympathetic figure, saying in sentencing documents that the meat packing mogul "cheated a bank and others out of a staggering amount of money - more than $26 million," and thus qualifies for a life sentence. A spokesman for the U.S. Attorney in Northern Iowa told ABC News his office has been monitoring the campaign to influence the sentencing hearing, which is scheduled for Wednesday, and officials there are concerned by it.

"There seems to be an orchestrated effort to spread misinformation and raise people's concerns falsely about this case," said Bob Tig, a spokesman for the U.S. Attorney's office in Iowa. "We're seeing thousands of emails, we've seen recent letters by a former congressman. There's an insistent thread of misinformation that runs through all of it."

The campaign to characterize prosecutors as zealous and seed doubts about the fairness of a life sentence, overseen by Rubashkin's Washington, D.C., legal and public relations teams, has enlisted help from five of the nation's former top law enforcement officials, Attorneys General Nicholas de B. Katzenbach (President Johnson), Ramsey Clark (Johnson), Edwin Meese III (President Reagan), Dick Thornburgh (Reagan), and William Barr (George H.W. Bush). Help for Rubashkin has come from both sides of the political aisle, even though his political giving largely focused on Republican candidates and causes.

Rubashkin's attorney said that the reason these officials have been willing to attach their names to this cause are clear – proposing a life sentence for a $26 million fraud case appears by most measures to be a disproportionate sentence, just the latest example of what she called unfair treatment of her client.

Indeed, the behind-the-scenes campaign is the latest strange twist in a case that has been unusual from the start.

It began to unfold on May 12, 2008, with a massive immigration raid on Rubashkin's Agriprocessors Inc., then the nation's largest kosher slaughterhouse and meat packing plant. At the time, it was the largest single raid of a workplace in U.S. history. Using Blackhawk helicopters and armed agents in combat fatigues, authorities arrested 389 workers for lacking documentation.

But the prosecution that followed eventually centered less on the immigration violations than on what prosecutors described as a massive financial fraud used to help prop up the business. It involved fake invoices, fake bills of lading, forged signatures and multiple sets of books, prosecutors said. They said Rubashkin "participated in the execution of the fraudulent schemes in an extraordinarily personal way," and said he lied to authorities and obstructed justice once he was caught.

Prosecutors argued for Rubashkin to be held without bail, triggering an outraged response from some quarters of the Jewish community. They argued that prosecutors were setting a dangerous precedent by calling for Rubashkin to be detained because of Israel's Law of Return, which grants automatic citizenship to every Jew.

The law of return was exploited in 1997 by Samuel Sheinbein, who fled to Israel days after the charred, dismembered body of Alfredo Tello Jr., 19, was found in an empty Maryland garage. At the time of Mr. Sheinbein's hasty departure from the United States, Israeli law barred the extradition of Israeli citizens for trial abroad. As a result of the furor over the case, the law was changed to make it easier for prosecutors to extradite citizens from Israel. Sheinbein accepted a plea bargain from Israeli prosecutors and is serving a 24-year prison sentence in Israel.

The Anti-Defamation League argued that prosecutors in the Rubashkin case could be setting a dangerous precedent that could be used to deny bail to Jewish defendants solely on the basis of their religion.

Whether that verdict warrants a life sentence, though, has become a subject of fierce lobbying from both sides.

Alan Dershowitz, a Harvard Law professor who helped develop the sentencing guidelines, wrote to U.S. District Judge Linda R. Reade on April 20 to express "distress" with the prosecutor's "misuse of the guidelines to try and secure a sentence well in excess of what Mr. Rubashkin's actions, as well as his personal background, deserve."

Rubashkin's lawyers have taken it further. In an April 11 letter to Assistant Attorney General Lanny A. Breuer, Nathan Lewin wrote that he has "never heard of, or witnessed, as vindictive, excessive, and mean-spirited a criminal prosecution."

Breuer responded that he and others "looked into your allegations last week, and saw no reason to revisit" them. Officials at the U.S. Attorney's office in Iowa told ABC News they followed a clear formula, laid out in the guidelines, to reach the conclusion that a maximum life sentence would be appropriate.

"Looking at the facts of this case, and then applying those guidelines to those facts, it appears his advisory guideline range would be in a range of life in prison, just because the facts are so egregious," Tig said.